Zac Efron, who played lead character Troy Bolton, didn't join the rest of his costars to reminiscence about the film, and a new report claims it's because of onscreen love interest and real-life ex Vanessa Hudgens!

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Part of the cast at the HSM reunion.

“Zac wanted to go to the HSM reunion," a source says of the 28-year-old. But he ultimately didn't go because Vanessa "did not want him there.”

After meeting on the musical's set in 2005, the duo dated for five years before calling it quits. “The last time the two were at an event together she was not comfortable because [her] new boyfriend isn’t cool with Zac,” the source tells OK! magazine.

Zac Efron (Troy Bolton)

The 28-year-old has a bunch of news movies coming out this year including Dirty Grandpa with Robert De Niro and Julianne Hough, Neighbors 2: Sorority Rising with Seth Rogen and Dave Franco, and Mike and Dave Need Wedding Dates with Anna Kendrick and Aubrey Plaza. He and his girlfriend, model Sami Miro, recently celebrated their one-year anniversary together.

KayCee Stroh (Martha)

The 31-year-old has taken a break from acting to focus on being a mom. She's married to producer Ben Higginson and they just welcomed their second child together, daughter Lettie Louise, in 2015. Their other daughter Zetta Lee is two-years-old.

Chris Warren Jr. (Zeke)

In 2013, the 26-year-old was involved in a messy lawsuit with his parents, claiming that they stole hundreds of thousands of dollars from him while he was still a minor. He ended up winning the case and got most of his money back.